--output-dir

[WillieRuemmele]

What does this PR do?

adds the --output-dir to project retrieve source
matches --retrievetargetdir from force * retrieve

What issues does this PR fix or reference?

@W-13207990@

see the original PR: salesforcecli/plugin-source#624

[shetzel]

QA with dreamhouse-lwc project

✅ bin/dev project:retrieve:start --source-dir force-app/main/default/classes --output-dir ret1 --> ERROR: --source-dir=force-app/main/default/classes cannot also be provided when using --output-dir
✅ bin/dev project:retrieve:start --package-name foo --output-dir ret1 --> ERROR: --package-name=foo cannot also be provided when using --output-dir
✅ bin/dev project:retrieve:start --metadata ApexClass --output-dir ret1 --> SUCCESS
✅ bin/dev project:retrieve:start --manifest package-classes.xml --output-dir ret2 --> SUCCESS
✅ bin/dev project:retrieve:start --manifest package-classes.xml --output-dir force-app --> ERROR: The retrieve target directory [force-app] overlaps one of your package directories. Specify a different retrieve target directory and try again.